In the industrial processing of gases and vapors it is often desired to remove small entrained quantities of liquids and solids. Such phase separations are commonly used both in manufacturing process and to prevent the discharge of pollutants to the atmosphere.
One typical application involves the separation of entrained liquids, such as water and oil, from air streams. For instance, a machine tool may generate much mist and fog, as well as solid dusts. Such kinds of contaminants are generally referred to herein as particulates. To prevent pollution of the surrounding areas, fans or blowers are often used to draw room air through the machine housing and carry it to a separator device where the entrained particulate is removed from the stream.
Fabric mesh filters and electrostatic precipitators are among the many devices favored to capture very fine entrained material from an airstream, sufficiently to meet environmental standards. However, when the particulate loading is heavy, such devices can become unduly loaded up and require frequent servicing. Therefore, impingement separator devices may be placed upstream to remove coarser particulate, and thereby produce a more useful system.
Generally, an impingement separator removes liquid (or solid) particulate from a gas stream by causing the stream to flow against the surface of an obstruction. Due to the large momentum of the particulate relative to the gas, the entrained material hits, rather than goes around, the surface of the obstruction. It thus loses its momentum through the impact, and collects upon the surface of the obstruction. It will then ordinarily aggregate with other droplets and flow by gravity to a collection point. Solid particulate can be similarly collected.
There is a large variety of known configuration for impingement separators. An essential impingement separator comprises a nozzle directed against a flat plate placed at right angles to the nozzle. An effective impingment separator is one which gives the desired separation with minimum energy consumption and has low cost and ease of servicing. Nozzles do not fit well with this standard of efficiency, and a common inpingement separator will thus be comprised of an array of simpler shapes, such as bars or vanes, and the like, placed in the gas stream to present a tortuous flow path. Typically, these are wavy, zig-zag, or chevron shaped sheet metal struts. See FIG. 18-144 of Perry, Chemical Engineers Handbook, 4th Edition, McGraw Hill, New York (1963pk ).
A typical prior art separator consists of a multiplicity of parallel chevron vanes across which fluid flows transversely within a rectangular housing. While such a configuration is suitably applied for use with electrostatic precipitators (which are similarly rectanguloid), it is not suitable for other applications. In particular, it is not convenient to use where relatively small diameter conduits carry gases at relatively high velocity, such as characterize the machine tool application mentioned above. When rectanguloid separators are so-applied to a small round duct, the gas must be be diffused and distributed evenly within the rectanguloid vane array, to achieve even low velocities and good separation with low pressure losses. The housing and ducting to achieve this are bulky.
For round line-duct applications, the impingement separator housing will desirably be circular and short in length, with the inlet and outlet co-aligned. Impingement separators have been designed in the suitably circular configuration, but they have not embodied the simplicity and efficiency that characterizes chevron vanes and the like. For example, U.S. Pat. Nos. 552,572 to Austin and 4,214,883 to Raseley et al. show compact devices but they are relatively inefficient in that they comprise simple flat plates. U.S. Pat. Nos. 2,157,829 to Metzgar and 4,014,671 to Andro et al., show how gas is caused to flow across a surface of revolution, which comprises a machined surface. Such are substantially more complicated and heavy to construct, compared to sheet metal vanes.
Thus, there has been a need for improvements in impingement separators. Especially, there has been a need for a low cost line-duct device, such as one which can be simply made from sheet metal, and which provides efficient separation and low loss of fluid stream pressure. There is a need for a separator which is compact and suitable for mounting into small circular conduits, especially in combination with existing filter type separators.